the whole thing was answered when you stated that the indica's were the flowering plants while the sativa is still in pre-flower stage...
Indica grow of shorter stature than sativa and take generally 50-70% shorter time to finish than sativa

some sativa can take up to 4 months to finish.
Indica's can finish in 6 weeks...

Now if you are getting 15 hours of light...???

Just wanted in on the discussion. lw